The present invention is useful in many graphics co-processors. The system can be used to improve raster imaging in many applications, particularly when the desired output can be described in part using geometric primitives. Many printing devices are controlled by page description languages, including Adobe Systems' PostScript.RTM. language, Hewlett Packard's PCL.TM., Canon's LIPS, NEC's NPDL and other languages by Kyocera and Xerox.
In a preferred embodiment, the system is used to implement Adobe Systems PostScript commands. Adobe Systems is the assignee of the subject invention. The PostScript system was developed to communicate high-level graphic information to digital laser printers. It is a flexible, compact and powerful language, both for expressing graphic regions and for performing general programming tasks. The preferred embodiment of the system of this invention is described in the context of a PostScript printer, typesetter or image-setter.
The PostScript language, use and applications are thoroughly described in a number of books published by Adobe Systems Inc., including PostScript Language Reference Manual (Second Edition) and PostScript Language Program Design. PostScript and related page description languages are useful with typesetters, image-setters, color printers and high throughput printers as well as high-resolution video or other display devices.
Printing, video display and other such devices are sometimes called marking devices or marking engines. A raster image processor (RIP) associated with a marking engine converts input information and commands into a rasterized (bit-mapped) region suitable for display on the associated output device. Commercially available devices include the Apple LaserWriter.RTM., the Linotronic.RTM. 100 and 300, the Adobe Atlas RIP and the Emerald RIP. A marking engine may use vertical or horizontal scan lines, but for convenience only horizontal scan lines are described here. The same or similar methods or devices can be used for vertical scan lines.
Some raster image processors use a graphic accelerator chip. One such chip is the Hitachi ARCTC chip, which can implement simple fills of rectangles and circles, simple line drawing, bit blitting and many Boolean combinations of these functions. NEC's 7220 chip also is popular, but cannot render complex geometric features. Hyphen has announced a graphic coprocessor chip, but that device is not yet publicly available for analysis.